Everything You Need to Know about Narcissists, Psychopaths, and Abuse - click on this link: http://www.narcissistic-abuse.com/faq1.html
Pathological narcissism has been compared to the Dissociative Identity Disorder (formerly the Multiple Personality Disorder). By definition, the narcissist has at least two selves. His personality is very primitive and disorganized. Living with a narcissist is a nauseating experience not only because of what he is - but because of what he is NOT. He is not a fully formed human - but a dizzyingly kaleidoscopic gallery of mercurial images, which melt into each other seamlessly. It is incredibly disorienting.
It is also exceedingly problematic. Promises made by the narcissist are easily disowned by him. His plans are ephemeral. His emotional ties - a simulacrum. Most narcissists have one island of stability in their life (spouse, family, their career, a hobby, their religion, country, or idol) - pounded by the turbulent currents of a dishevelled existence.
Thus, to invest in a narcissist is a purposeless, futile and meaningless activity. To the narcissist, every day is a new beginning, a hunt, a new cycle of idealization or devaluation, a newly invented self.
There is no accumulation of credits or goodwill because the narcissist has no past and no future. He occupies an eternal and timeless present. He is a fossil caught in the frozen lava of a volcanic childhood.
The narcissist does not keep agreements, does not adhere to laws, regards consistency and predictability as demeaning traits. The narcissist hates kiwi one day - and devours it passionately the next.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 3 DVDs with 16 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)